In bacteria the optimal concentration level of metal ions is controlled by transcriptional metalloregulators. The CueR (Cu efflux Regulator) protein regulates the intracellular amount of CuI-ion in several strains of bacteria. This member of the MerR protein family also operates by an activation mechanism based on a conformational change of the DNA-bound protein upon metal ion coordination. This also affects the structure of the DNA and therefore, RNA polymerase can initiate the transcription of the regulated genes leading to the formation of proteins the role of which is the removal of metal ion from the cell. The CueR protein gives a transcriptional response only for singly charged transition metal ions (CuI, AgI and AuI).
The purpose of our work is to solve the structure of the CueR protein in complex with an unflavoured divalent metal ion, the strong binder HgII. In that case we could compare the structural differences with the already available protein structures containing monovalent metal ions. Thus would help the understanding of the structural details of bacterial metal ion regulatory mechanisms on molecular basis. For this purpose we have optimized the conditions of the CueR protein expression and purification in E. coli, and set up a crystallization screen with similar conditions as described in the literature. The results of these experiments are presented.